repl: make last error available as `_error`

This is pretty useful when trying to inspect the last
error caught by a REPL, and is made to be analogous to `_`,
which contains the last successful completion value.

PR-URL: https://github.com/nodejs/node/pull/18919
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Vladimir de Turckheim <vlad2t@hotmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Prince John Wesley <princejohnwesley@gmail.com>
Reviewed-By: Shingo Inoue <leko.noor@gmail.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/doc/api/repl.md b/doc/api/repl.md
index 873e7449f5..c868106f2f 100644
--- a/doc/api/repl.md
+++ b/doc/api/repl.md
@@ -142,6 +142,12 @@ global or scoped variable, the input `fs` will be evaluated on-demand as
 ```
 
 #### Assignment of the `_` (underscore) variable
+<!-- YAML
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/18919
+    description: Added `_error` support.
+-->
 
 The default evaluator will, by default, assign the result of the most recently
 evaluated expression to the special variable `_` (underscore).
@@ -162,6 +168,17 @@ Expression assignment to _ now disabled.
 4
 ```
 
+Similarly, `_error` will refer to the last seen error, if there was any.
+Explicitly setting `_error` to a value will disable this behavior.
+
+<!-- eslint-skip -->
+```js
+> throw new Error('foo');
+Error: foo
+> _error.message
+'foo'
+```
+
 ### Custom Evaluation Functions
 
 When a new `repl.REPLServer` is created, a custom evaluation function may be